The present invention relates to power returnable coilable rules, and more particularly, to connections between the coilable power spring and a fixed hub.
Power returnable coilable rules have enjoyed considerable success in the marketplace and are very widely employed. Generally, such rules have a power spring providing the retracting force to draw the metal rule inwardly of the casing and effect its coiling thereabout. In some such rules, the spring operates to effect rotation of a reel to which its outer end is connected, and its inner end is engaged with a fixed hub about which the reel rotates. In some instances, the projecting end of the spring is bend about the hub to secure it thereto.
Since there are substantial forces exerted upon the connection of the spring to the hub, it is desirable that there be a positive engagement therebetween to locate the spring in a fixed position relative to the hub and essentially to preclude inadvertent disengagement.
It is an object of the present invention to provide an improved power returnable coilable metal rule in which there is a novel and secure interengagement between the inner end of the spring and the hub about which the reel rotates.
It is also an object to provide such a coilable metal rule in which the elements may be economically fabricated and readily assembled to provide such secure engagement between the rule and spring and the hub.
Another object is to provide such a coilable rule in which the end of the spring is precisely positioned relative to the hub.
Still another object is to provide such a coilable rule in which the hub and power spring may be readily assembled by automated procedures.